phil34

I was curious how the OBD reported water temperature compares with the instrument panel displayed temperature. So I installed my OBD "ScanGauge" to check it out. That answer is the displayed temp is not too close to the OBD temp at the high end. For example OBD =203F while instrument panel says 190F and OBD says 216F while instrument panel says 200F. This correlates with other's observations noted elsewhere on the forum.

But, back to the title of this posting. While driving I noted that the ScanGauge battery voltage usually indicated 12.6 volts and the battery would occasionally take sips of indicated 14.4 volts. When going downhill the 14.4 voltage was constant and the green "Charge" bar on the instantaneous mileage display was illuminated. I am new to this ride so that was a bit of a surprise. The car had been on the CTEK charger prior to the journey so the battery was fully charged when setting off. My conclusion of this charging behavior while driving is that the charge algorithm only energizes the alternator as required or to take advantage of a downhill run.

I suppose this behavior is well known to others on the forum but it was a bit of a surprise to me.

CaliBenzDriver

Congratulations, now you know the many different numbers that mislead many into thinking everything is okay.

The AGM lead-acid battery is being charged anytime voltage is above 12.55V.

When driving on 12.6V the ALT is controlled to produce "float voltage" with a near zero charge current.

Below 12.4... 3.. 2....1...0.... 11.9V that's a battery being drained to supply the chassis power instead of ALT: ouch!

phil34

Thanks for the informative replay. With interest I have viewed most posts in the oil pump solenoid thread. You have contributed greatly there.

Might I ask where you got the details on the 12v charging scheme? Out of curiosity I have searched and came up with mostly conjecture or foolishness.

CaliBenzDriver

The best place to source the most relevant documents for your chassis is through WIS.
With that knowledge you'll understand how things should work.

The alternator output is managed by ECU to supply all chassis power while charging AGM with a variable profile.

phil34

Thanks. I have WIS/EPC SW. I have only used EPC. I must delve WIS.

CaliBenzDriver

Yes please! These systems are pretty sofisticated in their own individuality.
Bosch technologies are the backbone of these chassis.

I find that performance diagnosis is limited as is the case with CAN-C ESP/ECU/TCU Latencies.

Given enough time you'll dig deeper into interesting topics.